drm/amd/display: Rename dml2_wrapper.c to dml2_wrapper_fpu.c

drm/amd/display: Rename dml2_wrapper.c to dml2_wrapper_fpu.c

[WHAT]
This function is an FPU compilation unit. Therefore it's not
allowed to call DC_FP_START/END functions. It currently does
so and we'll need to move those functions out. Therefore
rename the existing compilation unit so we can introduce a
non-FPU dml2_wrapper.c.

Reviewed-by: Austin Zheng <austin.zheng@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Hung <alex.hung@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>